Portion of a toothbrush



FIG. 1 is a top, front, left perspective view of a portion of a toothbrush showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a top view thereof; and,

FIG. 6 is a bottom view thereof.

The uneven-length broken lines represent the bound of the claim and form no part thereof. The even-length broken lines showing the remainder of the portion of a toothbrush are for environmental purposes only and form no part of the claimed design. 

CLAIM The ornamental design for a portion of a toothbrush, as shown and described. 